A customer service agent at a Covered California call center in Concord, Calif., waves a flag for technical assistance during the opening day of enrollment of the Patient Protection and Affordable Care Act, Tuesday, Oct. 1, 2013.

Washington — The first 24 hours of Affordable Care Act (ACA) signup were marked by delays and glitches, as millions of Americans flooded government websites to check out the new health-insurance marketplaces – and, in some cases, sign up.

The irony is that opponents of the new program may have contributed to the flood, as their focus on trying to delay or defund the program helped to advertise it to the public. Instead, as Senate Democrats stood firm in opposing legislation to fund the federal government that also defunded or delayed the ACA, the government went into partial shutdown.

But it wasn’t the shutdown that caused the glitches in the launch of the marketplaces. The ACA, or Obamacare, is largely funded outside the annual appropriate process. Still, it would be easy for the public to link the flawed launch of Obamacare to the shutdown, since they began the same day – and then blame Republicans, whom polls suggest will bear the brunt of blame for a shutdown.

“Consider that just a couple of weeks ago, Apple rolled out a new mobile operating system, and within days, they found a glitch, so they fixed it,” Mr. Obama said Tuesday. “I don’t remember anybody suggesting Apple should stop selling iPhones or iPads – or threatening to shut down the company if they didn’t.”

Federal officials told The New York Times that it wasn’t just high use that brought on the problems, but they did not elaborate. Healthcare.gov, the federal site that serves as the marketplace for more than 30 states, got 4.7 million unique visitors in its first 24 hours, the White House reports. No figures were released on how many people were able to sign up for coverage on the federal exchange.

White House officials offered assurances that the problems would be fixed as soon as possible.

“The team is ramping up responses, and making sure [the site] is ready for influxes of folks, so the process will get easier,” David Simas, deputy senior adviser for White House communications, told MSNBC Wednesday. “Tomorrow will be better, the day after will be better.”

The signup period lasts six months, until March 31, 2014. For coverage to begin on Jan. 1, people must sign up by Dec. 15.

States that chose to run their own exchanges have also experienced problems, at least in part due to high traffic. New York State reported several million visits to its site. The Maryland Department of Health and Human Services said its exchange had received 50,000 unique visitors by 4:30 p.m. Tuesday, despite “connectivity issues,” The Baltimore Sun reported. Some states put in place work-arounds. The Washington state exchange, WAhealthplanfinder.org, asked users to fill out a form and to wait for contact by phone, according to Kaiser Health News.

Republicans jumped on the problems as evidence that the ACA isn’t ready for prime time, and as a sign that the law itself is bad.

“These ‘glitches,’ which the President is trying to brush off, reveal how totally unprepared the government is for this launch even with three and a half years to prepare,” Rep. Darrell Issa (R) of California, chairman of the House Oversight and Government Reform Committee, said in a statement. “Now that Obamacare’s implementation has begun, more and more of the American people will turn to Congress looking for practical health solutions the bill does not deliver.”

The government shutdown is a direct result of Republican opposition to the ACA. The Republican-controlled House has refused to pass a “clean continuing resolution,” or CR – that is, government funding into the new fiscal year, which began Tuesday, without provisions that Democrats find objectionable. The Republicans linked government funding to measures that would either delay or defund the ACA and eliminate a tax that partially funds the program.

Obama will host a meeting of bipartisan congressional leaders at the White House at 5:30 Wednesday afternoon. There, he will call on the House to pass a “clean CR” to reopen the government and also to raise the debt ceiling, according to news reports. The federal government will reach the limit of its borrowing authority on Oct. 17, after which it risks defaulting on its debt.

“We’re pleased the president finally recognizes that his refusal to negotiate is indefensible,” said Brendan Buck, spokesman for Republican House Speaker John Boehner. “It’s unclear why we’d be having this meeting if it’s not meant to be a start to serious talks between the two parties.”